The present invention relates to an apparatus for testing motor oil. The apparatus has automatic temperature control means for a test plate and the oil to be tested. The oil level during operation is automatically compensated.
As is well-known, one of the most important characteristics for lubricating oils for internal combustion engines, and more particularly for compression ignition engines, is their heat-resistance. The higher the heat-resistance, the better is the capability of the lubricating oil to keep the pistons of the engine clean. Deposits and films generally form in the region of the first piston ring even when the engine is hot. The operating temperatures may sometimes reach values exceeding 230.degree. C.
The quality of suitability of an engine oil has to be checked by subjecting it to long-running tests effected directly in the engine. Such tests may take a hundred or even more hours each. After the test, the oil condition and piston appearance have to be checked.
Since such tests are expensive and time-consuming intensive, efforts are continuously made to find a less expensive and shorter laboratory test.
The apparatus of the state of the art for carrying out such tests generally include complex and costly installations which are based on the principle of spraying oil onto a test plate which is secured on the cover of a vessel containing oil, the test plate being heated by an electrical heating element.
The aforementioned test equipment has several drawbacks. The operating reliability of such equipment is relatively low; their selectivity is poor as well. Furthermore, the maintenance of such equipment is costly because the temperature of both the test plate and the oil to be tested as well as the compensation for oil losses caused by evaporation of its light-weight fractions must be closely supervised by an attendant. Apart from this, the equipment of the state of the art has certain limitations; for example, the temperature of the oil to be tested cannot exceed a value of 330.degree. C at the most and the duration of the complete test is also a factor to be considered. It has furthermore been ascertained that a rectangular shape of the test plate is disadvantageous since it is difficult to precisely manufacture such plates to perfectly fit the plate on the cover in order to seal it. Oil leakage into the space between the plate and the cover negatively influences the test results.